Science & Technology Department of Sichuan Province (2021YJ0115).

Houttuynia cordata is a well-known plant used for both medicine and food with good antibacterial and anti-inflammatory effects, so the species possess significant medicinal values. Modern studies revealed that volatile oil, flavonoids and alkaloids are known as the main components. These components showed bioactivities including anti-inflammation, anti-viral, anti-tumor, immune modulation, anti-oxidation and anti- bacteri. Monoterpene is an important type of volatile oil, and it is the key medicinal component for the species. Among different germplasm resources of H. cordata, there are obvious difference on components and contents of the oil, and the species could be divided into two types according to content of the monoterpene, namely M (high content) and D (low content). At present, it is not clear about biosynthetic pathway of terpenoids, as well as molecular mechanism of forming different chemical types which seriously restrict breeding of high quality varieties and its industrial development. In our previous studies, we had successfully cloned two genes encoding monoterpene synthases (HcTPS1 and HcTPS2), and found that there were rich alternative splicing in the germplasm resources of the different types. However, we do not know how the genes regulate biosynthesis of the monoterpene. So this study plan to explore function and expression pattern of HcTPS1/HcTPS2 and their alternative splicing both in vitro and in vivo via transcriptome analysis, prokaryotic expression, molecular docking simulation, enzyme activity analysis, genetic transformation, q-PCR and western blot, so as to reveal molecular mechanism of forming the different chemical types of houttuynia cordata. The present study would provide scientific evidences for breeding of high quality varieties of H. cordata and its cultivation, and promote biomedical healthcare industry in China.